About 4:25 p.m., Southwest Flight 709 from Norfolk, Va., arrived at the airport with a flight attendant in need of medical attention, officials said.

The flight had originated in Denver and was bound for Chicago and later Dallas, but its stop in Baltimore was scheduled, officials said.

"It arrived right on time," said Whitney Kidd, an airport spokeswoman.

The plane, which had 139 passengers and flight crew aboard, landed safely and passengers were never at risk, Kidd said.

Those bound for Chicago were able to board a different plane and depart Baltimore after only a slight delay, said Olga Romero, a Southwest spokeswoman.

Airport fire and rescue personnel responded to the plane as it taxied to the airport, then requested assistance from the Anne Arundel Fire Department's hazardous materials unit because of uncertainties about what had caused the illness, Kidd said.

A subsequent, though still preliminary, investigation indicated the attendant, who was not identified, became ill after smelling a bathroom air freshener spray that was on board the plane, Romero said.

It was not clear what form her illness took, but she was transported to a local hospital and has since recovered, Romero said.

"We know that she's in the clear now. She's OK," Romero said.

It was not clear why or how the air freshener had made the woman sick, Romero said.

Crews continued to investigate the incident until 6:27 p.m., when the plane and the area around it were deemed fully secured, Kidd said.

The disturbance did not affect any other flights at the airport, she said.